Small-scale laboratory reactors are commonly used to explore and conduct research into topics of interest associated with chemical reactions. Many different types of experiments can be performed to study reaction materials, reaction variables, processes associated with chemical reactions, and other aspects of chemical reactions. Reaction materials include chemical reagents, catalysts, catalyst promoters, catalysts inhibitors, catalyst supports, and reaction products. For example research may be conducted into factors that may affect the desirability and/or economic viability of using particular reaction materials, process variables, and/or manufacturing techniques to carry out commercially significant chemical reactions.
Many chemical reactions require or can be facilitated by presence of a catalyst in a reaction vessel. As is generally known, a catalyst is a substance that can facilitate a chemical reaction without itself being consumed in the reaction. Typically, a catalyst must come into contact with one or more of the chemical reagents to catalyze the reaction. Heterogeneous catalysts are in a different phase than the chemical reagents. Most heterogeneous catalysts are solid phase and act on liquid and/or gaseous reagents. One common technique for conducting reactions involving a heterogeneous catalyst is to place a porous catalyst basket inside a reaction vessel containing liquid and/or gaseous reagents. The catalyst is placed in the catalyst basket before the reaction is started.
The catalyst is typically dispersed on the surface of a catalyst support, such as pellets made of a zeolite or other suitable porous material. The catalyst support pellets form a catalyst bed in the catalyst basket. The basket is at least partially porous so the fluid reagents can pass through the basket and contact the catalyst in the basket. But the pores or openings in the basket are small enough to retain the catalyst support pellets in the basket. Thus, the catalyst is generally confined to the catalyst basket.
During the reaction, a mixing system may be used to mix the reagents and produce flow of the reagents through the catalyst bed. One type of mixing system includes a rotating stirrer (e.g., impeller) that stirs liquid phase reaction materials. The catalyst basket can remain stationary as the stirrer causes fluid reagents to flow radially outward through the catalyst bed. One example of this is in U.S. Pub. Application No. 20040042942. Another type of mixing system rotates the catalyst basket in the reaction vessel. The rotating basket performs the function of an impeller and stirs the fluid reagents while generating flow of fluid reagents through the catalyst bed in the basket.
Currently used reactors having catalysts baskets are often unable to obtain good gas-liquid mass transfer, particularly in relatively smaller-sized reactors (e.g., reactors having an internal volume less than about 2500 mL. In smaller-sized reactors the impellers need to be designed to allow for the physical presence of the catalyst baskets. The catalyst baskets also must be designed to hold a sufficient volume of catalyst. Consequently, because of the limited amount of space inside smaller-sized reactors, the effective blade diameter of the impellers is much less than ideal for generating good KLa values.
In order to obtain decent KLa values in smaller-sized reactors, high rotational rates for the baskets/impellers are required. However, shear forces increase as the speed of rotation is increased. In conventional reactors having catalyst baskets, the increased shear forces can degrade larger catalyst particles, generating fines. Fines are undesirable because they make results difficult to interpret during characterization of the system because the experiments are designed to study the intrinsic activity of the catalyst on large catalyst particles. When high speed rotary agitation is introduced to increase mass transfer, fine particles are generated and the reaction is a combination of slurry and large particle catalyst. The inability to achieve good KLa values in smaller-sized reactors sometimes leads scientists to conduct tests in larger reactors that more closely resemble a pilot reactor or production reactor. However, larger reactors require more materials and longer setup times. This is more expensive and increases the time required to bring new products to market.
Also, when there are both gas and liquid phase reagents it can be difficult to achieve good mixing of the gas and liquid phase materials in a reactor having a catalyst basket. The catalyst basket is typically at least partially immersed in the liquid phase. The conventional mixing systems direct liquid flow radially outward through the catalyst bed. Flow of the liquid phase in a radial direction does little to mix the gaseous phase into the liquid. In some cases the conventional catalyst basket can impede mixing of gas and liquid phase reagents, particularly to the portion of the liquid phase below the basket.
The inventor has developed improved systems and methods for mixing reaction materials in a laboratory reactor system, which will be described in detail below.